Boolean functions removed faces, is there a relatively quick way to fix this?
Blender can select non-manifold edges CtrlAltShiftM. The mesh analysis display options can also be useful for 3D printing.

You will find enabling the 3D Print Toolbox addon will be helpful. Click the Check all button to see how many locations have issues. While there is a Make Manifold button, be careful to check that the automated process doesn't add unwanted faces.



If you are in edit mode each item listed will be a button that will select the relevant areas.